These are the types of waves that do not need material medium for their propagation. They are produced by electromagnetic vibration. All the electromagnetic wave have the velocity of about 3 x 108m/s , but they defers in their wave length and in their frequency too. Therefore electromagnetic waves can be distinguished by their wavelengths and frequencies. Electromagnetic wave has the properties of diffraction and interference
Electromagnetic wave though produced differently most of them result from electron suffering some kind of energy changes. For example when electron are accelerated in aerial , radio wave s are emitted.
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The lists of electromagnetic wave below is done on the of their decreasing wave length
The Radio wave as electromagnetic wave has the longest wavelength, the wavelength varies from few millimeters to several kilometers. The Radio wave is emitted from a transmitters and carry radio signals to radio set
The shortest Radio wave is called microwaves. The long Radio wave wavelength travels by reflection through the ionosphere. The ionosphere consists of electrically charged gases which are very high above the Earth.
This electromagnetic wave know as Infrared wave, is found just beyond the red end of the visible spectrum. Infrared waves are present in radiation from the sun or from the filament of an electric lamp. They are easily detected by the sensation of heat.
The Infrared wave has wavelength of about 10-6m, and they can be reflected by polished surface, It can the also be detected by photographic film, and that is why picture can be taken in dark with Infrared rays.
The use of Infrared
- It is used in drying of painted item in manufacturing industrials
- Infrared is for treatment of muscular complaints
Light waves (Visible spectrum)
The light wave or visible spectrum is made up of red, orange, yellow, green, blue, indigo, and violet rays. When these rays combine together they form white light. In visible spectrum the red ray has the longest wavelength while the violet ray has the shortest wavelength
The main source of this electromagnetic wave (light wave) is sun
Ultraviolent rays (u-v)
This electromagnetic wave is located just beyond the violet end of the visible spectrum. The wavelength of ultraviolent ray is about 10-8m.
Ultraviolet rays are produced quartz, mercury filaments or sun. The ultraviolet ray can be detected by r florescence paper. It cannot pass through smoky atmosphere or window glass.
The wavelength of this electromagnetic wave ( x-ray) is in order of 10-10m. It has a shorter wavelength than Ultraviolet light and about thousands time shorter than the wavelength of those light waves. The x-rays, can ionize gases and also have a penetrating power that they can pass through substance opaque to the white light. x-ray can be diffracted by crystal but unaffected by either magnetic or electric field.
X-rays are produced when fast moving electron strike a metal target, which reduces their velocity.
Use of x-rays
- It is used in hospital to destroy abnormal growth
- It can be used to locate broken bone in the body
- It is used in industrial to detect cracks in metal
Note that much x-ray in body is harmful and can lead to sterility and adverse change in the blood
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Gamma-ray is also electromagnetic wave, the Gamma –ray is very similar to x-ray . The wavelength of Gamma-ray is in order of 10-11m . Like x-ray , Gamma-ray ionizes gases and darken photographic plate, but has more penetrating power than x-ray because of its shorter wavelength. Apart from the difference in wavelengths, Gamma-ray and x-ray differ in their origin. The Gamma-ray is emitted by radioactive substance, which arise in atomic nuclei whereas X-ray come from energy changes in the electrons outside nucleus.
Gamma-ray is also as useful as X-ray, but more dangerous then X-ray in excess of it.
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